1. Field of the Invention
The present invention relates to a semiconductor device comprising a contact plug having an elliptical sectional shape. For example, the invention relates to a semiconductor storage device such as a NAND flash memory.
2. Description of the Related Art
Conventionally, an electrically erasable and programmable read-only memory (EEPROM) is well known as a nonvolatile semiconductor memory, and the NAND flash memory is widely used as an EEPROM in which high integration can be achieved.
The NAND flash memory includes various circuits (hereinafter collectively referred to as a peripheral circuit) in order to program, read, and erase memory cell data. Recently, dimensions of a MOS transistor included in the peripheral circuit are shrunk with finer design rules of the memory cell. For example, Jpn. Pat. Appln. KOKAI Publication No. 2005-311131 discloses the shrinking of the dimensions of the MOS transistor. As a result, for example, an amount of current passed through the MOS transistor is reduced.